Heretofore in a screen assembly for a window or a door, there is no known control for closing off passage of air through the screen, except by closing the window or using a storm window mounted upon the inside or exterior of the screen assembly. Heretofore, screens have been employed upon the interior of a vehicle window with the flow of air therethrough controlled by raising or lowering the window as desired cutting-off air flow or progressively decreasing air flow through the screen. The disadvantage of this construction is that unless the window is substantially closed to prevent rain from entering the vehicle, very little ventilating air can through the screen. Heretofore in connection with window vents in the roofs of vehicles, it is known to employ a screen mounted within a suitable frame within the vehicle roof so that upon progressive opening of the closure window, controlled amounts of air can flow into the interior of the car through the roof vent.